Glass composition



July?, 1959 H. R. swlFT x-:TAL 2,893,882v

GLASS COMPOSITION Filed Dec. 1?. 1953 Shift In Futectic Position with 0.57.11' (-azozquiv.) '12,5 for' 0.57. Cao

8.5 M 72 Cao 14o 70310 A o5) 9.0 my z 7 w u t o d to/ '15.0 /Shiftlnutectic r( 0.11, sttutez for CaO molhstom\ 11.0 {zeem Jagd 1 l l l ATTORNEYS United States Patent O i GLASS COMPOSITION Howard R. Swift, Toledo, and Donald E. Sharp, Maumee, Ohio, assignors to Libbey-Owens-Ford Glass Company, Toledo, Ohio, a corporation of lOhio Application December 17, 1953, Serial No. 398,711

s claims.V (Cl. s-s2) '.(a) A satisfactory chemical durability (b) Good melting characteristics '(c) A suitable viscosity-temperature 4relationship (d) A reasonable expansion coefficient, and (e) A low liquidus temperature In considering the above properties, the necessity 'for a low liquidus temperature may not be readily apparent, but, it has been found in practice to be a very important consideration. Specically, the lower liquidus temperature permits the operators to cool the glass to lower temperatures immediately before fabrication without encountering devitrication difficulties. This in turn makes the glass more viscous and allows the glass to be drawn at a greater speed for a given thickness of sheet glass.

Heretofore, to attain some of the above mentioned characteristics and in particular to attain a low liquidus temperature along with -good melting characteristics, it has been customary practice to increase the soda content of the batch. Although the 'addition of the soda gives a lower liquidus temperature and better melting characteristics, it has been found to detract from the overall quality of the glass and to give poorer chemical durability and a high, unsatisfactory, coeicient of expansion.

In like manner, it has been found that the use of optimum quantities of aluminum oxide, calcium oxide, and

magnesium oxide will give a satisfactory chemical durability, a reasonable coeicient of expansion and a suitable viscosity-temperature relationship. However, in using these optimum quantities of aluminum oxide, calcium oxide, and magnesium oxide, a high silica content must be used to obtain the optimum low liquidus temperature which high silica content in turn causes the melting characteristics to become unsatisfactory because of the formation of a melting scum. Thus, it will be noted that an increase in several desirable characteristics or properties is Obtained only at a reduction in other desirable properties and the overall characteristics of the batch are not substantially improved.

It is therefore a primary object of this invention to produce glass compositions having good chemical durability and melting characteristics, a suitable viscositytemperature relationship, a low liquidus temperature, and a reasonable coefficient of expansion.

A further object is to provide a glass of special composition having those characteristics set forth above which is adapted for continuous production in large quantities in accordance `with conventional methods and apparatus used in the manufacture of sheet glass. Y

I 2,893,882 Patented July 7, 1959 It is to be pointed out that the development of this invention came about by our desire to find what quantities of the beforementioned ingredients of 'aluminum oxide, calcium oxide, magnesium oxide, sodium oxide, vand silica would give the optimum durability, expansion, and crystallization resistance properties without regard to the optimum meltability and viscosity characteristics. Having found these specific quantities, we then discovered that the labove-named desirable resulting properties could be retained and at the same time the melting characteristics and the viscosity-temperature relationvship could be substantially enhanced by lowering the silica content of the batch while at the same time adding, within certain narrow ranges, deiinite quantities of certain non-metals and their compounds, such as tluorine and phosphorous -which have the property of causing glass to become substantially opalescent to visible light radiation when Iused in large quantities.

-While it has been well known that iluorides act as mineralizers and generally improve the melting characteristics when added to conventional glass compositions, and that phosphorus pentoxide may be substituted for soda to improve the melting characteristics, they were both generally believed to cause an increase in the liquidus temperature of the glass. Contrary to this belief, we have found that under certain conditions and within certain ranges of composition the results are quite different from previously held opinion and practice. Broadly, we utilize narrow ranges of iluorine Or phosphorus pentoxide to shift the eutectic combination towards lower levels of silica and thus obtain all of the beforementioned desirable properties.

In the accompanying drawings:

Fig. 1 is'a triaxial diagram showing the shift of phase boundaries of various glass compositions when uorine is added to the batch; and

Fig. 2 is a diagram of the type shown in Fig. 1 showing the phase shift when phosphorus pentoxide is used.

To best illustrate what happens to the crystallization temperature when tluorine is introduced in a series of soda-lime-ma-gnesia-silica type glasses reference is made particularly to Fig. 1 which illustrates by relative position the combination of three Vvariables which total a constant sum vat all times. In this example, the variables are the CaO, MgO, and Si02 contents of the glass, the crystallization temperatures for which we have indicated by means of isotherms in Pig. 1. In particular, this gure represents the superposition of two diagrams, one illustrating a series of glasses without iuorine, and the other la series of .glasses with 0.5% iluorine and iixed minor ingredients as shown in glass vII of Table I below. For simplicity in presentation, only the 1800 F., 1840 F., and 1880 F. isotherms are shown, but other isotherms could be located by interpolation or extrapolation since these isotherms follow the same general pattern. The isotherms are represented, in Figs. l `and 2, by dotted and solid lines, the dotted lines in Fig. l representing the isotherms of the composition containing F and, and in Fig. 2, of the composition containing P205. The solid lines in Figs. l and 2 represent the'isotherms of the original starting glass compositions.

In the diagram of Fig.y 1 Vit will be noted that 0.5 iiuorine causes a marked shift in the location of the eutetic composition in this series, particularly in regard `Table I as Glass I, to the composition indicated both below and on the diagram as Glass ll, when 0.5% tiuorine is added to the Glass I composition, the isotherms for the shifted position being shown in dotted lines.

Liquidus, Temperature,n F

As will be apparentfrom the above table, `the :presence of 0.5% fluorine in Glass II lowers the silica content necessary for the eutectic by 1.7%. This fis .a zmarked Sand unexpected shift which `permits us to4 obtain glass compositions with excellent crystallization properties without usingan excessively high-silica content. Furtherfrnore,it will be noted thatzthe MgO'content of the eutectic remained constant while the. silica .and calcium roxide 'contents of the eutectic composition are substantially changed.

In addition vto the lowering of the silica content, it will -be apparent that an extra benetit was also :realized in the case of the liuoride'additions in-,that the liquidus temperature of the eutectic was lowered 12 F.

lt has been Afound that an almost linear change :in the location of the phase boundaries towards a lower silica content has taken place as a result of the `incorporation where the narrow range of iiuorine has been foundtolbe between 0.15% and 1.1% 'iluorine and the silica range to kbe from 69.8% to 73.4%.

As a further advantage we have'found thatthe` crystallzation of such glasses containing silica-and fluorine as determined by the abovel relation can be additionally improved by adjusting the magnesium oxidecontent to'fall yin the range`3.8% to 4.2%.

Glass compositions which are located in the tridymite `iield and which havelluorine or silica contents outside of the limits set forth aboveV Willremain in their original trdyrnite. field with Ythe `incorporation of fluorne, while .at the same time, their liquidus temperatures nare increased markedly. For example, the glass composition A indicated .below has its Vliquidus temperature raised over 100 F. to that indicated in compositionB as uorine is substituted for fthe CaO without change in-the=SiO2 content.

TABLE II Oi equiv Primary Phase n the other hand, the addition of lluorine to glasses which were originally in the wollastonite and diopside ields Will iirst have `the eifect of decreasing the .liquidus temperature, after'which, further additions will change the primary phase to tridymite and the liquidus temperature will then increase. Thus, 'it will he'noted that the proper amount of fluorine to' be added to A-thetglass-toobshows tain the beforementioned crystallization benefits is quite critical.

As there are a number of Ways of determining the percentage of iiuorine in glass compositions, it is to be noted that the amount of uorine in the above composition refers to the amount in the final glass as determined by chemical analysis. And, lin order that the percentages of fluorine given herein .as determinedbyanalysis may have a definite specic meaning invew of the fact that analytical methods for determining the presence of combined uorinefin glass are not-well developed, the method. of analysis for uorine in glass bywhich these results `were obtained and whichvwill henceserve tointerpret the results is hereby given. This method is as follows:

(l) Fuse one gram of minusllfmesh glass in a platinum crucible with 1.5 grams of Na2CO3. Commence the fusion on a Meeker burner. Transfer to a blast burner and fuse at low-temperature `for l0. minutes. Swirlthe melt in the Crucible and allow to cool with the platinum 'lid on the Crucible.

(2) Transfer to a 250 mlfbeaker halfiilled Withwater. Allow to soak for 2 hours. Stir and break `up the particles often during the 2-hour period. Bring to boil .with stirring and then crush the particles with a flattened glass rod. A

(3) Allow to settle and then decant'the supernatant liquid through a large No. 40 Whatmanlter paper Well packed with pulp. Catch the :filtrate in a 250..-ml.volu metric flask. Wash the residue withhot .watenuntiltthe flask is nearlyfull. .Coolfand bring fthe filask vto volume.

(4) A 50 ml. aliquot is taken -for the .uorine deter- .mination This solution is placed in .a ml. tall-form .beaken Ten Vdrops of Alizarin kRed 'S indicator are added. l-l HC1 is added d ropwise until the Asolution turns yellow. 2% NaOH is added until a pink lcolor l-50 HCl is added u ntil the solution just turns yellow. One milliliter of butter isadded. The solution is mechanically stirred while standard thorium `nitrate Ais added dropwise. The endpoint is reached when the first permanent pink color shows.

(5) To calculate the percent of uorine in the glass, -multiply theml. of thorium reagent 'usedby its tiuorine equivalent by 500. To findthe oxygenequivalent ofjiiuorine multiply the percentage of fluorine by 16/ 38 or .421. `l'his'is to Ibe subtracted from Vthe total in reporting the complete analysis.

Preparation of reagents .Standard `Naf" solution-Prepare standard lsc lutitgn from a C.P. NaF salt. Strength of solution is 5.7;-500 grams per liter or 0.0026 gm. F2 per ml.

Thorz'um nitrate- 13.8 grams are madeA up toalitcr "with water. standardize againststandard NaFvrsolution using procedure for iiuorine in a glass, eliminatinggthe .preliminary fusion.

invention, namely the addition of phosphorusrpentoxide instead of uorine to a vglass composition.

Asbeforementioned, phosphorus pentoxide may lalso-be used to produce the results of our invention, and to Ab es't illustrate the changes that vtakeplace in the crystallization tem- .perature when this oxide is introduced into Va seriesnof ..soda-lirne-magnesia-silica type glasses..reference is'fmade to Fig. 2. As is clearly shown in the .diagram,vthe..a ddi tion of 0.5% phosphorus pentoxide also causes-amarked shift :inthe location of the eutecticV compositiompauticularly in regardkv to., the silica and CaO contentsrotthe eutectic. YItwill be noted that the compositionrwith the .tlowestcrystallization temperature is shifted -fromthe composition indicated below and on the diagramas Glassl also/aaah to that indicated as Glass III bothbelow and ,on the diagram when 0.5% phosphorus pentoxide is added to the series. This shift is quite similar tothat achieved by the uorine although the-amount bf reduction Iin the eutectic silica content is somewhat less for theaddition of 0.5%

P205 than for the addition: of'0;5% tluorine.`

In considering the above TableIII it'will'be noted that the MgO content of the eutectic remained substantially the same for both eutectic compositions illustrated, while the silica and calcium oxidecontents of-the eutectic composition were substantially changed. Andfas beforein the case of the uorine, the transposition of the respective phase boundaries is found to be almost linear with the incorporation of phosphorus -pentoxide yso th'atit is possible to select the -amount of phosphorus pentoxide for optimum crystallization resistance solelyon the basis of the silica content ofthe glass. Likewise, it has been found that the crystallization characteristics of any sodalime glass canv be improved by selecting the.fsilica and phosphorus pentoxide to satisfy the following relationship: Percent Si02=73.7i0.22.0 (percent P205) `where the phosphorus `pentoxide contentranges from 0.25%

to 1.95% and the silica:range isjfrom"69.8% tol 73.14%.`

As before, a still furtheradvantagehas been found in that the crystallization ofv such'4 glasses containingsilica and phosphorus pentoxide as determined by the'above relation can be additionally improved by adjusting the magnesium oxide"con`tent to Vfall vin'the range 3.8% to 4.2% as in the case of iluorine'.l

Now as a third embodiment of ourinvention we have found that the elects of iluorine 'and phosphoruspentoxide are additive and that they'combine readily'to give the beforementioned desirable properties. The i exactrelationship between'the respective' elements hasbeen found to be the combination of the newly=established constants of 3.4 (percent F )'4 and -2.0 (percent"P2O5 )c asvused inthe independent equations employing 'tll'loijinetand phosphorus pentoxide respectively, the combination equation 1 being: Percent Si02=73.7i0.23.4 (percent F)t2.0' '(percent P205) for the limits of Si02 between 679.8% and 73.4%. In this equation, 'for the Amaximum y perkeritage of Si02 (73.4%) where AF is present -with Vonly trace amounts of P205 the amount of F used is approximately 0.15%. Where only trace amounts of F arefused the P205 percent is approximately 0.25.

Compositions where the maximum percent Si02 is present along the mixtures of F and P205 will vary as to the mixtures of F and P205 from 0.15% F and 0% P205Y to 0% F and 0.25% P205 and', the effects of the F and P205 being additive, the percent F -andppercent-P205will be determined for any intermediate mixture between the above-recited limits by the combined -eqnation.- Thus, where 0.075% F is used at a SiO, level of 73.4% the percent of P205 present in admixture with the F is:

Percent P205:

3.4)( percent F=2.0% P205. Thus,thepex"cent` SiO;y level may be adjusted when F is used admixture P205 'by substituting for part of the F in the limits of 0.15 to 1.1%, an equivalent percent of P205. By way of example,

where the Si02 level is at a maximum of 73.4% and only 0.075% F is used, an amount of `P205 equivalent to the additional 0.075% F necessary to lower the Si02 to 73.4% must be added along with the F, and as 2.0Xpercent P2O5=3.4 percent FV the equivalent amount of P205 which must be'added equals By way of further example, selecting a value of Si02, we know that, in accordance with the following equation 1.09% F must be present when F is used alone.

Percent Si02= 73.7(102) 3.4 (percent F) 70.0: 73.7(i0.2) 3.4 (percent F) t Percent F==3.7/3.4 or 1.09

Where only .30% F is used, then an amount of'P205 equivalent to .79% F must be used in combination with the F and this may be determined lby either of the following methods:

3.4 (percent F substituted for) 2 l Percent P205= Percent P205= or 1.34

Percent sio2=73.7(io.2)3.4(percent P) nomment P205) 70.0=73.7 (i0.2) -3.4(0.30)-2.0 (p e r c e n t l P205) Y Y Percent P205= 1.34

4found that the relationship is relatively unaffected by the other ingredients as long as they are at customary levels, -that is between 6% to 12% CaO, 0% to 2% A1203, 12% to 15% Na20 and 0% to 0.6% -Fe203. It is also-obvious that the sum total of all of the ingredients must be 100% and consequently the content of A1205, CaO, and Na20 plus any ingredients in minor quantities such as S05, B203, K2O, Fe203,Ba0 or other oxides of the second group of the Mendeletf table must represent theV difference. By minor amounts we mean less than 1% of such minor ingredients.

As pointed out previously, the eiects of iluorine and phosphorus pentoxide are additive and combinable in that either may be used alone or in combination with the other. However, we have found that there are certain low limits for the tluorine and phosphorus pentoxide contents wherein the Vgain in desirable properties is too slight to ibe ofcommercial importance. These limits as men tioned hereinabove are approximately 0.15% lliuorine and 0.25% phosphorus pentoxide.

Similarly, it has been found that certain high limits of these non-metals or their compounds cannot be exceeded without causing the glass to become opalescent or even substantially opaque to visible light radiation. We have also found that the amount of iluorine or phosphorus pentoxide vaporized and lost is relatively greater for large .additions ofthe materials. Considering=these factors, we have found the upper limit by weight of iluorine to be 1.1% iluorine, and the upper limit .of phosphorus pentoxide to be 1.95%.

Likewise, there are also limits of silica below and above iwhichit not desirable togo because-of ncreaSedcOsts,

@saggia-.8.3

.loss of durability, .or increased-melting scum, .all of Whioh aro dotfinoontal in .ono way .or another' to o maso-produ@ of thofslass isin ,tho amount .as prooorihod by our iomluls withthe addition .of llorine ,and phosphorus .pentorgide By way of illustration, several other typical compositions utilizing silica vquantities as determined by our 'In-further consideringv .glasses made according Yto our 'ffiornaulos oroavon :in-.tablier form ioTablolY 1.0

TABLE IV A. Glass compositions 1,5 y Material Glass IV GlassV Glossy! L- eto, 12. s 71. 7 7o. 4 A1105 1. 0 0. 7 1. 5 Cao `vS35 19.2 f9.3 Mgo-. 4..1 Y f3.9. o Naio-- 13.3 1&2 12.9 T.20 K10--. 0.-1 0.1 0.2 so.- 0.3 0. 2 0.3 .1F 10.35 .-0.25 .Orequiv 10.1.5 :0. 1 'P101 1-.0 1.25 Liquidns'Temp., 1, 796 1,8104 1813 B. Balch compositions;corresponding to the `rb ove Glass IV GlassrV Glass VI Y:1.0 sand 1,000 1, 000 1,000 Apure 58 42 94 Caleinrn Limestone 40 '63. 32 Dolor'nite Limestone. -269 Y25 275 Soda Ash. 130s 308 311 salt oaks--- -12 12" 12 Florspar. 2o 15 l Bone .Ash 31 41 ing ingredients orbe made ultraviolet-,absorbing .thrqugh theuseof ceria, titania, or infra-red absorbingbyithe use .of ferrousroxidre without aiecting the relationships set :.forth .in the lformulas.

And, although several embodiments have -fbeerr de- .scrifbed,.itfis -to be understood Vthat the forms of the in- --ventiondisclosed hereinare to be taken as fthe preferred Aembodiments thereofand that-variouschanges may be resorted to `without.departing from-the spiritof v,theinvention. or `fthe-scope of the-following claims.

with'the above composition having the 'SQzandfiinxa iixedrelative relation substantially as determined-'bythe "following oquotionr APercent `SiO2=73:7 i0:2-3.4(percent VF) 2. A glass com-position inaccordance yWith-claim ..1 vin gwhich P3505 `is substituted lfor part ofthe theramount 'of' 'P205 being -determined by the following equation:

3.43)( (percent Fl substituted afor) I Percent P205: 2

Cil

r8 .fixed roletvmeltion .as determined by the fouowing .Qqrutillg Y.elastno..o11.1.1150Sitio@Ysorrentina t essentially of the following ingredients the: ranges given:

Percent Si02 -....Y 69.8 to 73.4 .PercentMgO 3.8 .to 4.2 Percent CaQrj: 6 to 12 -Pertcentlslag 12 to 15 Piel-cent AIRQS f. 0 to 2 VPercent 0 to .6 Percent minor ingredients O to 1 jlercent P119@ n `0.25 to 1.95

with tho .ahorn Composition..havingfihe-.SiOz,and P205 in .av ixed..relative.1e1ationsubstantially as determined vby .the fqllnwinslaqution:

` -4. A`glass'f-composition consisting essentially of the following ingredients -uI :the proportions substantially as "given:

35 .and-rhoiitieoflisudus @metrature of about 17.92 F- .comp n consisting essentially of the j iollonns' dienstig .tliofnronortioos .substantially as :.wcg:

`.Percent S1191... 72'7 Percent CO l 7.9 .Percent 4-2 APfsl'F-"fnt-49012534.. 1-3 oroontbll.. 13-2 PoroontSOa-, 0-2 fRoro-ootlaQs... 0-5

aandghaying ,axliquidus `tgnxlperatu-1"e of about 1810 F. tA osition consistingessentially of the fole kproportions substantially as -andf1having-`aliqnidlis-temperature ofgabout 1796 F. '17-1A"fsisszoooirotitonoonistios'essentially of tho Ilfollovvinggngredientsin thelpreportions substantially as gwen;

PorsoooiQa 11.7 Percent A1395 w 0.7 Percent 'lCaO 9.2 Percent MgO 3.9 Percent NazO 13,2 Percent KQO Bercex'xtzSQg 8. A glass composition consisting essentially of the Percent-F 0.25 following ingredients in the proportions substantially as Percent-O2 equiv. 0.1 given: Percent P205 1.25

percent Si()2 70 4 5 and having a liquidus temperature of about 1813 F. 532:22; lgs References Cited in the le of this patent Percent MgO 4.0 UNITED STATES PATENTS Percent Nago 12.9 2,262,951 Lyle Nov. 18, 1941 Percent K2O 0.2 10 2,508,070 Lyle May 16, 1950 Percent S03 0.3 2,552,495 Poole May 8, 1951 

1. A GLASS COMPOSITION CONSISTING ESSENTIALLY OF THE FOLLOWING INGREDIENTS WITHIN THE RANGES GIVEN: 